Fluorbuergerite

specimen number:
2133199

location:
Mexquitic, San Luis Potosi, Mexico

description:
Sharp lustrous brown crystals measuring to 0.9 cm in size on matrix. In good condition. Good example for this classic Mexican material.

The Mexquitic locality, situated in the state of San Luis Potosi, Mexico, is the type locality for the rare tourmaline species fluor-buergerite. Geologically, this mineral occurs within small cavities in a highly silicified, topaz-bearing rhyolite flow. The fluor-buergerite (a complex iron-aluminum borosilicate) formed during the late-stage cooling of the volcanic rock, appearing as small, dark bronze to black, lustrous prismatic crystals that are often deeply striated. Historically, the material was first described in the mid-1960s based on specimens collected by local prospectors, and the mineral was officially named in honor of the crystallographer Martin Buerger. Unlike large-scale commercial mines, this was a very localized occurrence found in weathered rhyolite outcrops, and significant production was limited to a brief period in the 1960s and 1970s. Because the original discovery sites have yet to be rediscovered and the locality is now widely considered "lost" to modern collectors. Specimens in circulation today are almost exclusively from old collections, valued for their historical significance as the definitive representative of the species.

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